Collaborations (Details) (USD $)
 3 Months Ended 1 Months Ended 10 Months Ended 1 Months Ended 6 Months Ended 12 Months Ended 1 Months Ended 3 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Dec. 31, 2014
Aug. 31, 2012
Nov. 30, 2011
Oct. 31, 2011
Jun. 30, 2001
Dec. 31, 2009
Jun. 30, 2011
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2011
Oct. 31, 2013
Dec. 31, 2015
Collaboration and other revenue $ 196,100,000 $ 181,200,000                        
Revenue 4,644,700,000 4,683,100,000                        
Research and development 1,039,300,000 1,109,300,000                        
Nonoperating Income (Expense) 92,700,000 56,000,000                        
Marketing, selling, and administrative 1,523,500,000 1,484,900,000                        
Acquired in-process research and development 256,000,000 0                        
Amortization of Intangible Assets 154,200,000 131,900,000                        
Bi Compounds [Member]                            
Nonoperating Income (Expense)     92,000,000                      
Lly Compounds [Member]                            
Acquired in-process research and development     55,200,000                      
Erbitux [Member]                            
Net product sales 13,800,000 13,200,000                        
Collaboration and other revenue 74,400,000 77,700,000                        
Revenue 88,200,000 90,900,000                        
Effient [Member]                            
Net product sales 121,800,000 119,300,000                        
Amylin [Member]                            
Proceeds from prepayment of revenue-sharing obligation       1,210,000,000                    
Trajenta (BI) [Member]                            
Revenue 82,300,000 76,900,000                        
Tanezumab [Member]                            
Acquired in-process research and development 200,000,000                          
Sales [Member] | Amylin [Member]                            
Collaborative Arrangement, Rights and Obligations Percent         15.00%                  
Sales [Member] | Outside the United States [Member] | Exenatide [Member]                            
Collaborative Arrangement, Rights and Obligations Percent           100.00%                
Revenue Share [Member] | Amylin [Member]                            
Collaborative Arrangement, Rights and Obligations, Terms       (1,260,000,000) (1,200,000,000)                  
Revenue Share [Member] | United States [Member] | Amylin [Member]                            
Collaborative Arrangement, Rights and Obligations Percent         65.00%                  
Revenue Share [Member] | Outside the United States [Member] | Amylin [Member]                            
Collaborative Arrangement, Rights and Obligations Percent         35.00%                  
Secured Note [Member] | Amylin [Member]                            
Debt Instrument, Interest Rate, Stated Percentage         9.50%                  
Profit and Development and Marketing Share [Member] | Effient [Member]                            
Collaborative Arrangement, Rights and Obligations Percent             50.00%              
Research and Development Exp [Member] | Baricitinib [Member]                            
Collaborative Arrangement, Rights and Obligations Percent               30.00%            
Milestone Payments [Member] | Solanezumab [Member]                            
Collaborative Arrangement, Rights and Obligations, Terms                 70,000,000          
Milestone Payments, Development and Regulatory [Member] | Lly Compounds [Member]                            
Collaborative Arrangement, Rights and Obligations, Terms 187,500,000                 (62,500,000) (50,000,000)      
Milestone Payments, Development and Regulatory [Member] | Amylin [Member]                            
Collaborative Arrangement, Rights and Obligations, Terms         (150,000,000)                  
Milestone Payments, Development and Regulatory [Member] | Trajenta (BI) [Member]                            
Collaborative Arrangement, Rights and Obligations, Terms                       478,700,000    
Milestone Payments, Development and Regulatory [Member] | Jardiance (BI) [Member]                            
Collaborative Arrangement, Rights and Obligations, Terms                   300,500,000 97,200,000      
Milestone Payments, Development and Regulatory [Member] | Baricitinib [Member]                            
Collaborative Arrangement, Rights and Obligations, Terms 415,000,000                          
Milestone Payments, Development and Regulatory [Member] | Tanezumab [Member]                            
Collaborative Arrangement, Rights and Obligations, Terms                         350,000,000  
Milestone Payments, Sales-based [Member] | Baricitinib [Member]                            
Collaborative Arrangement, Rights and Obligations, Terms 150,000,000                          
Milestone Payments, Sales-based [Member] | Tanezumab [Member]                            
Collaborative Arrangement, Rights and Obligations, Terms                         1,230,000,000  
Royalty Agreement Terms [Member] | Solanezumab [Member]                            
Collaborative Arrangement, Rights and Obligations, Terms of Arrangement, Period                 10 years          
Royalty Agreement Terms [Member] | Baricitinib [Member]                            
Collaborative Arrangement, Rights and Obligations Percent               20.00%            
Upfront Payment [Member] | Amylin [Member]                            
Collaborative Arrangement, Rights and Obligations, Terms         (250,000,000)                  
Collaborative Arrangement [Member]                            
Marketing, selling, and administrative $ 49,300,000 $ 48,000,000                        
Subsequent Event [Member] | Sales [Member] | Erbitux [Member]                            
Collaborative Arrangement, Rights and Obligations Percent                           38.00%